1. Field of the Invention
The present invention relates generally to die cutter blankets and, in particular, to boltless locking arrangements for die cutter blankets.
2. Description of the Prior Art
Rotary die cutting is a process wherein either a continuous web or single sheets of material, e.g., corrugated paper or cardboard, is traversed by way of roller sets or rollers within a differential pressure plenum through the die-cutting machine. Ultimately, this material is passed through a set of rolls, which consists of the die cylinder and the anvil cylinder. A cutting die, which is made up of cutting knives and scoring rule, is mounted on the die cylinder. The anvil cylinder is covered with a removable resilient material, typically referred to as an anvil blanket. The cylinders rotate about parallel axes. As material being processed passes between this set of cylinders, the cutting die penetrates through the material and into the anvil, producing the intended product.
Anvil blankets are flexible covers that wrap around the rotating anvil cylinder. They are typically constructed of a thin sheet metal liner, however, wire, plastic or nylon mesh is also functional. Structural locking members are attached to one or both ends of the liner, and an elastically resilient material, such as urethane, is molded to the outer surface of the assembly. The blankets are built in a variety of sizes; circumference, length, thickness; which complies with the machinery manufacturers"" specifications for anvil cylinder construction. Typically, a plurality of blankets is used to cover the length of a standard anvil cylinder.
The anvil cylinder is typically constructed of steel or cast iron. However, the anvil cylinder arrangement may also consist of the basic cylinder surrounded by a series of one-piece or multi-piece slip bearings. The anvil cylinder or slip bearing arrangement is supplied with a channel running parallel to the axis of rotation. This channel is used to attach and mount the anvil blanket to the cylinder. In cooperation with the channel, the blanket is designed with an engaging mechanism to secure the blanket to the cylinder.
An example of a die cutter blanket may be found in U.S. Pat. No. 5,916,346 to Neal, which discloses a typical engagement mechanism for securing the anvil blanket to the anvil cylinder via a channel. The prior art anvil blanket has an engagement mechanism on either edge of the blanket. This engagement mechanism consists of a male member on one edge of the blanket, and a female member on the other edge of the blanket. The male member mates with the female member which, in turn, fits into the channel of the anvil cylinder.
One drawback of the prior art is the structural inadequacies involved with three mating elements. For example, in using the prior art engagement mechanisms, after the female member is inserted into the channel, the normal force used in locking the male member into the female member may cause the female member to become dislodged from the channel. Further, the structure of the prior art engagement mechanisms is such that the cutting die (or knives) are moved along the blanket at a constant pressure. However, when the cutting die reaches the anvil cylinder channel area, the cutting die may not fully cut the material due to the lack of rigidity of the engaged male and female members of the blanket in the channel. One solution to this problem is to increase the pressure of the cutting die, ensuring that it will fully penetrate and cut the material uniformly across the entire perimeter of the anvil cylinder. However, this increased pressure will result in excess cutting and wear of the blanket, resulting in increased maintenance costs and downtime.
It is therefore an object of the present invention to provide a cylinder cover that overcomes the deficiencies in the prior art. It is another object of the present invention to provide substantially continuous rigid support around the perimeter of the anvil cylinder, particularly across the channel. It is a still further object of the present invention to provide an easily engageable and disengageable engagement mechanism that provides secure attachment of the blanket to the anvil cylinder. It is yet another object of the present invention to provide an engagement mechanism for a die cutter blanket that is simple in its installation and maintenance in the field.
Accordingly, I have invented a cylinder cover which is particularly useful as a die cutter blanket. This cylinder cover includes an engagement mechanism, which interacts with a channel having two opposing sides and a base. The cylinder cover includes a flexible blanket with two ends, with each end configured to abut when the blanket is circularly wrapped around a cylinder, e.g., an anvil cylinder. The present invention also includes a female member attached to one end of the blanket; the female member having a leg connected with and opposing a resilient engaging element by a base member. This resilient engaging element is configured to frictionally engage a side of the channel. Also included in the present invention, is a substantially rigid male member attached to the other end of the blanket.
In a first embodiment, the cylinder cover includes a flexible sheet metal liner having an outer side and an inner side, the flexible sheet metal liner outer side is integrally formed with an inner side of the urethane material. In addition, the female member includes an indentation and the male member includes a projection, such that, in use, the indentation and projection penetrate one another and are frictionally engaged. The female member indentation is attached to the outer surface of the flexible sheet metal liner, and the inner surface of the female member leg is attached to the inner surface of the flexible sheet metal liner. In a second embodiment, the engagement mechanism of the cylinder cover is adapted to engage a slip bearing sleeve, covering an outside surface of an anvil roller, the slip bearing sleeve having a channel with two opposing sides and a base. This embodiment also includes a channel insert within the channel and a male member indentation configured to accept and compress the resilient engaging element against the side of the channel insert. In this second embodiment, the resilient engaging element is a loop structure. It is this loop structure that the male member indentation is configured to compress against the side of the channel insert.
In operation, the female member is inserted into the channel and engaged therein. Next, the blanket is wrapped around the cylinder and the male member inserted into the female member, locking the blanket around the cylinder. When the male and female members are engaged with the channel, the blanket is substantially continually supported by a rigid substrate; the anvil cylinder and the male member.
While the present invention may be utilized with any cylinder having an appropriately sized channel, the cylinder cover of the present invention is particularly suited for use with an anvil roller. Further, the anvil roller may be surrounded by a slip bearing sleeve, the slip bearing sleeve fully covering the anvil roller. This slip bearing sleeve can have a channel, similar to the anvil roller, wherein the female and male members may be engaged. In addition, the channel on the slip bearing sleeve may also have a channel insert which is configured to frictionally receive and contact the female member of the blanket.
The present invention, both as to its construction and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of specific embodiments when read in connection with accompanying drawings.